Cooking of food morsels

ABSTRACT

Surface water is removed from morsels of water-impregnated food (e.g., washed raw potato slices) before subsequent dehydration and cooking bypassing the morsels downwards through cold oil and draining off the separated water.

s m M {J1me Stares ate a {151 3,649,306 Dalgleish [45] Mar. 14, 1972[54] COOKING OF FOOD MORSELS [72] Inventor: James McNair Dalgleish,Warwick, En- [56] References Cited gland UNITED STATES PATENTS [731Assignee Gdde Nmhams 2 853937 9/1958 Pm "99/407 gland 3,396,656 8/1968Forkner... ....99/z46 [22] Filed: July 28, 1969 3,535,l28 10/1970Willard ..99/246 [211 App! 845390 Primary Examiner-R0bert W. JenkinsAttorney-Larson, Taylor & Hinds [30] Foreign Application Priority DataAug 8, 1968 Great Britain ..37,985/68 [57] ABSTRACT Surface water isremoved from morsels of water-impregnated l Cl /2 4/ 9/104, food (e.g.,washed raw potato slices) before subsequent 99/207, 99/339, 99/403dehydration and cooking bypassing the morsels downwards [5 l 1 Int. Cl lw ..B65d 9/00 through old oil and draining off the separated water, [58]Field of Search ..99/246, 251, 252, 404, 405,

18 Claims, 7 Drawing Figures PAIENTEDMAR 1 4 I972 SHEET 2 [IF 3 COOKINGOF FOOD MORSELS The water-impregnated morsels are heated in hot oil atthe bottom of a dehydration section to convert the water in them tosteam, and the steaming morsels then rise to the top to enter a cookingsection where they are cooked in the steam which rises with them.

This invention relates to the cooking of morsels of certain foods whichcontain water and may also have water on their external surfaces.

Example of such foods are peeled potato cuttings which have been washedin water ready for conversion into fried potato products such as potatocrisps or sticks. Other examples of such foods are certain com-basedproducts for cooking to form snack foods, and pieces of raw meat.

In the manufacture of potato crisps it is common practice to peel thepotatoes, slice them and wash the slices in cold water before plungingthem into a long horizontal bath of hot vegetable oil to dehydrate themand also cook them. The slices must be thoroughly washed to remove thestarch grains from the cut cells on the surfaces of the slices, becauseotherwise the starch will gel in the hot oil, the slices will tend tostick together, and also the starch will affect heat transfer in the hotoil circulating system. However, some of the washing water tends toenter the bath with the slices and has to be steamed off, thusincreasing the heating load of the cooker. If attempts to remove thewashing water are made by devices such as vibrators, rollers or driptrays, they are only partially effective and tend to produce clingingtogether of the slices which makes the subsequent task of dehydrationmore difficult. Because the oil circulating through the bath requires tobe well above the boiling point of water and because the cooking of therelatively small amount of dehydrated solid potato matter requireslittle heat compared with the latent heat heat required to turn thewater into steam, any entrained water represents an even greaterproportion of extra heating load with no corresponding increase in theoutput of crisps. Furthermore, the high oil temperature and therelatively short cooking time require considerable skill from theoperative if he is to avoid discoloration or darkening of the crisps dueto the chemical reaction of the sugars in the potato matter. This isbecause during the dehydration phase the heat from the oil converts thewater in the slices to steam at atmospheric pressure. Therefore thesolid matter is surrounded with steam rather than oil and tends toexperience a temperature of only about 100 C. during the initial phaseof conversion into steam. When the rate of conversion subsequentlydiminishes, the temperature of the solid matter rises towards that ofthe oil and darkening soon follows. Also, the oil starts to pervade theslice because the steam no longer keeps it out.

There are other disadvantages. The sudden immersion of the cold slicesin the hot oil tends to produce blisters which may puncture and entrapoil. To enable the required heat transfer to take place, the oil mustcirculate quickly but on the other hand the progress of the slicesthrough the bath must be slowed down by mechanical retarders. Inaddition, dunking devices must be provided to force the rising slicesdown under the surface of the oil. This in turn demands cleaning theretarders and dunking devices in order to remove any trapped slices.

The present invention seeks in its various aspects to avoid one or moreof the above-mentioned disadvantages.

According to one aspect of the invention, there is provided a method ofremoving surface water from water-impregnated morsels of food before themorsels are dehydrated in hot oil, wherein the morsels are passeddownwards through a bath of oil to cause the surface water to separatefrom the morsels, the oil in the bath is cold compared to the hot oil,and the separated water is removed from the bath.

Preferably, the cold oil is in one leg of generally U-form ducting, thehot oil is in the other leg, a bend section connects the lower ends ofthe two legs, and the separated water is drained off from the bdndsection.

According to another aspect of the invention, there is providedapparatus for cooking water-impregnated morsels of food which comprisesan upwardly extending dehydration section having a bottom inlet for themorsels and connecting at its top end with a cooking section, and meansfor introducing hot oil into the dehydration section at such atemperature that, in operation, water in the morsels is turned intosteam, the morsels and the steam rising in the dehydration section toenter the cooking section where heat from the steam is used to cook themorsels.

Preferably, the cooking section surmounts the dehydration section andprovides at least one extended cooking path for the morsels.

The dehydration section preferably forms one leg of generally U-formducting, the other leg which is a dewatering section has a top inlet forreceiving morsels of water-impregnated food which also have water ontheir surfaces, and means are provided for removing water from thebottom of the ducting.

According to a further aspect of the invention, there is provided amethod of cooking water-washed slices of potato in ducting of generallyU-form which is partially filled with oil, comprising the steps of:

a. passing the slices downwards through one leg of the ducting whichcontains cold oil so as to separate the washing water from the slices,

b. passing the dewatered slices through a bend section which connectsthe two legs of the ducting and removing the separated water through anoutlet in the bend section,

c. heating the slices at the bottom of the other leg in hot oil toconvert water in the slices into steam so that the slices and the steamrise to the top of the hot oil,

d. picking up the rising slices in a cooking section mounted above thehot oil,

e. causing the slices to ascend an extended path in the cooking section,

f. using heat supplied by the steam to cook the slices,

g. and removing the cooked slices from the cooking section By way ofexample the invention will not be described with reference to theaccompanying diagrammatic drawings of which:

FIG. 1 is a vertical section through a cooking apparatus of generallyU-form,

FIG. 2 is a vertical section through another cooking apparatus ofgenerally U-form,

FIG. 3 is a side view of the oil-filled portion of the apparatus of FIG.2,

FIG. 4 is a detail modification shown in vertical section,

FIG. 5 is a perspective view of the apparatus of FIG. 2 but showing acooking section provided with three spiral elevators,

FIG. 6 is a plan of the embodiment of FIG. 5 showing a common dischargefor the elevators, and

FIG. 7 is a cross section through the embodiment of FIG. 5 showingdouble points of pickup for the elevators.

Referring to FIG. 1, the generally U-form apparatus comprises adewatering section 10 with a top inlet 11 for receiving food morsels, adehydration section 13, a bend section 12 which connects the sectionsl0, l3, and a cooking section 14 which surmounts the section 13. Thesection 10 is filled with cold oil and forms a cold leg whilst thesection 13 is filled with hot oil and forms a hot leg. The section 14uses steam which has been generated in the food morsels in the section13.

The bend section 12 is provided with a well 16 for the removal of waterwhich is protected by a perforated floor 17 to prevent morsels of foodentering the well. A valve 9 controls the removal of water from thewell. The section 13 is divergent in the upward direction so that itscross section increases as it approaches the cooking section 14. At thetop is an annular manifold 20 with a perforated inner wall forwithdrawal of oil. The section 13, manifold 20 and an injection 18 formpart of a circulation system for hot vegetable oil which includes ascreening tank 23, a pump 24, a heat exchanger 25 for heating the oiland a valve 26.

The cooking section 14 is provided with a metallic spiral elevator 28having a stem which projects downwards for a short distance into thesection 13 in order to be immersed in and heated by the oil. Theelevator is arranged to be given a high-frequency, low-amplitudeoscillation about its vertical axis via mechanism in a housing 29supported by radial struts from the surrounding walls of the section 14.The mechanism may for example be pulsed hydraulically from an externalpump. The spiral flight of the elevator 28 cooperates with a spiral wallvane 30 to slow down the rise of the steam through the section 14. Thetop of the elevator flight extends through a side outlet 31. An oilarrester 34 which permits the passage of steam is located below a steamstack 35 provided with an adjustable damper 36.

To produce potato crisps for example, the apparatus may be operated inthe following manner. Firstly, the sections 10, l2, 13 are filled withcold oil, the oil in the section reaching an upper level opposite themanifold 20. The heat exchanger 25 is then brought into operation sothat the temperature of the oil injected into the section 13 reaches therequired temperature, say 175 C. The oil in the section 10 which remainsrela' tively static compared with the forced circulation through thedehydration section 13 does not rise appreciably in temperature and iskept cold by potato slices washed in cold water which are then fed tothe inlet 11. The potato slices sink down the column of relatively coldoil in the section 10 because they are denser than the oil. Water has agreater density than oil and during the descent of the slices theirsurface water separates from them, runs down the section wall or sinksto the bottom and is drawn off through the perforated floor 17 and well16. Consequently such water does not reach the section 13 where it wouldotherwise occupy space and absorb heat during its conversion into steam.In addition, the removal of the water from the external surfaces of theslices results in a reduced tendency for the slices to stick togetherand in a quicker heating of the slices when they reach the hot oil inthe section 13. The cold slices which are dropped into the section 10experience a small rise in temperature as they proceed to the section 13but no formation of steam occurs before the hot oil injector 18 isreached. During continuous operation, the oil in the duct 10 reaches atemperature of about 5 C. near the inlet 11 and about 20 C. at theupstream end of the bend section 12.

The slices which contain a high proportion of water in their inner cellspass through the bend section 12, become heated by a jet of hot oilissuing continuously from the injector 18 and rise to enter the section13. Their oil coating promotes the transfer of heat from the hot oil totheir cells and water therein is converted into steam which formsbubbles adhering to the slices. The buoyancy of the steam bubblesassists the rise of the steaming slices to the top surface of the hotoil. Because the steam is generated under oil pressure it is initiallyat a saturation temperature above 100 C. and it becomes superheated. Thedivergent shape of the section 13 slows down the rise of the hot oil andslices to match the reducing rate of steam generation and so increasesthe transfer of heat from the oil to the slices. It also compensates forthe loss in effective flow area due to the projecting stem of theelevator 28. As the rising slices reach the surface of the hot oil, theyare picked up by the flight of the elevator and are constrained tofollow its spiral extending path to the top of the elevator.

The oil at the top of the section 13 is at about 160 C. and is muchhotter than either the slices which may still contain a little water orthe steam at that point; if the slices were to remain in the oil to becooked such cooking would be too quick and would lead to discoloration.Accordingly, section 14 is pro vided for cooking the slices more slowlyat the much lower temperature of the superheated steam.

The pressure within the section 14 where final drying and then cookingtake place is virtually atmospheric but because of the oil pressure inthe section 13 the steam (formed at say 103 C.) which rises into thesection 14 is superheated steam (say at 1 10 C.). This steam which isreceived from the slices supplies the heat required for cooking in thesection 14.

The extended path of the conveyor flight which the slices are forced tofollow ensures sufficient time for drying and cooking them. For examplethe slices which may take only a few seconds to rise up the section 13are forced to remain for about three minutes in the section 14. Finally,the dried and cooked slices which are now crisps are discharged throughthe outlet 31 into a receptacle or chute whilst the steam rises throughthe oil trap 34 to be discharged through the stack 35.

It will be seen that the hot oil system is substantially a closedcircuit system with the divergent section 13 serving as a largereservoir for the oil. Once the slices enter the oil in the preliminarydewatering section 10, they travel wholly immersed in oil or insuperheated steam until they reach the outlet 31. The elevator 28provides lift through the cooking section 14 at a controlled rate. Thusthe whole treatment of the slices can be closely controlled. It will benoted that the cold washed slices are not plunged into a dehydrationbath of hot oil but are dewatered and warmed before they meet the hotoil of the dehydration section.

Referring to FIGS. 2 and 3, the apparatus is basically similar to thatshown in FIG. 1 and comprises a ducting of generally U-form having adewatering section 40 with a top inlet 41 for the washed food morsels, abend section 42, a divergent dehydration section 43 and, surmounting thelatter, a cooking section 44 housing a spiral elevator 45.

The section 40 which is the cold leg of the ducting and is inclineddownwards towards the dehydration section 43 is provided with awater-cooled jacket 46 for possible use during startup of the apparatus.

The bend section 42 includes a flattened or fishtail portion 48 in whichoperates a hinged flap 49 which is adjustable between a closed settingfor excluding hot oil from the cold leg 40 during startup and an opensetting in which it together with the shape of the portion 48 cooperateto hamper any movement of hot oil towards the cold leg.

The bend section 42 provides a perforated floor 51 above a well 52provided with a controlled outlet 53 for draining off water which hasseparated from the food morsels during descent of the cold leg 40. Thefloor 51 has a slight depression and faces the bottom inlet to thesection 43.

The section 43 which is the hot leg of the ducting and is verticalconstitutes a reservoir forming part of a hot oil circulation systemsimilar to that described with reference to FIG. 1. An annular manifold55 leads to an oil outlet 56 but there are two hot oil inlets providedin parallel, viz. a main inlet 57 and below it an auxiliary inletprovided by an injector 58 which faces the floor 51. The purpose of theinjector 58 is to direct a curtainlike jet of oil against any foodmorsels which may tend to collect on the floor 51, e.g., cold morsels atstartup, thereby heating them and causing them to rise and enter thesection 43. The injector 58 may be operated continuously with the maininlet 57. An oscillatory elevator 45 in the section 44 provides a doublespiral path for the food morsels picked up from the top of the section43. To facilitate such pickup, an annular deflector 61 extends inwardsfrom the wall of the the section 43 and is shaped to deflect risingmorsels over the top of the adjacent sidewall of the elevator flight.This has the advantage that it provides an annular pickup instead of apoint or doublepoint pickup. The deflector is perforated to permitpassage of the rising steam.

in the preferred modification shown in FIG. 4, the end section 42connecting the cold and hot legs is formed with a small bottom shelf 64against which brush the blades of a rotatable star-wheel or rotarypaddle 65 which lies in a restricted passage near the bottom end of thecold leg 40. The star-wheel which may be positively driven will permitfood morsels to pass down the section 42 but will obstruct any flow ofhot oil past it to the cold leg. The auxiliary hot oil injector 58 ofFIG. 2 is replaced by an auxiliary injector 66 which also directs acurtainlike jet of hot oil towards the floor 51 but with a downstream ortargential component of motion. The disturbances created by theoperation of the star-wheel 65 and the injector 66 keep the floor 51clear of deposits of food morsels.

FIGS. 5 and 6 show a grouping of their spiral elevators 70 arranged inparallel above the dehydration section 43 and having the tops of theirflights arranged to feed a common outlet 71 for the crisps or othercooked food morsels. The use of more than one elevator in the slowcooking section permits an increased output from the apparatus.

FIG. 7 shows how the three elevators 70 with double flights may havedouble pickup points 72 which are arranged at the top of the section 43,each pickup point lying in one of six notional concentric paths.

1 claim:

1. Apparatus for cooking water-impregnated morsels of food whichcomprises an upwardly extending dehydration section having a bottominlet for the morsels and connecting at its top end with a cookingsection, and means for introducing hot oil into the dehydration sectionat such temperature that, in operation, water in the morsels is turnedinto steam, the morsels and the steam rising in the dehydration sectionto enter the cooking section where heat from the steam is used to cookthe morsels, said cooking section surmounting the dehydration sectionand providing at least one extended cooking path for the morsels, saidextended path being provided by a vibratable spiral elevator.

2. Apparatus according to claim 1, wherein the spiral elevator has astern which extends downwards into the dehydration section.

3. Apparatus according to claim 1, wherein a deflector is provided atthe top end of the dehydration section for deflecting rising morselsinwards on to the elevator flight.

4. Apparatus according to claim 1, wherein the elevator has a doublespiral flight.

5. Apparatus for cooking water-impregnated morsels of food whichcomprises an upwardly extending dehydration section having a bottominlet for the morsels and connecting at its top end with a cookingsection, and means for introducing hot oil into the dehydration sectionat such a temperature that, in operation, water in the morsels is turnedinto steam, the morsels and the steam rising in the dehydration sectionto enter the cooking section where heat from the steam is used to cookthe morsels, said cooking section surrnounting the dehydration sectionand including a plurality of vibratable spiral elevators which provideextended cooking paths in parallel relationship for the morsels.

6. Apparatus for cooking water-impregnated morsels of food whichcomprises an upwardly extending dehydration section having a bottominlet for the morsels and connecting at its top end with a cookingsection, means for introducing hot oil into the dehydration section atsuch a temperature that, in operation, water in the morsels is turnedinto steam, the morsels and the steam rising in the dehydration sectionto enter the cooking section where heat from the steam is used to cookthe morsels, said dehydration section forming one leg of generallyU-form ducting, the other leg which is a dewatering section having a topinlet for receiving morsels of water-impregnated food which also havewater on their surfaces, and means for removing water from the bottom ofthe ducting.

7 Apparatus according to claim 6, wherein the ducting adjacent the lowerend of the dewatering section has a section which is is shaped torestrict the entry of oil from the dehydration section to the dewateringsection.

8. Apparatus according to claim 6, wherein a rotatable starwheel isprovided adjacent the lower end of the dewatering section and arrangedto restrict the entry of oil from the dehydration section to thedewatering section.

9. Apparatus according to claim 6, wherein the dehydration section isvertical and the dewatering section is inclined downwards towards thedehydration section.

10. Apparatus according to claim 6, wherein a bend section of theducting which connects the two legs provides a perforated floor above anoutlet for draining off water.

11. Apparatus according to claim 10, wherein the perforated floor formsa shallow depression which faces the bottom inlet of the dehydrationsection.

. Apparatus according to claim 10, wherein a nozzle is provided fordirecting a jet of hot oil against the floor.

13. Apparatus according to claim 12, wherein the nozzle is inclined inthe direction of motion of the morsels across the floor.

14. Apparatus for cooking water-impregnated morsels of food whichcomprises an upwardly extending dehydration oil section having a bottominlet for the morsels, a bottom inlet for oil, a top outlet for themorsels and a top outlet for oil, the dehydration section being part ofa hot oil circulating system and forming a straight section whichpermits a free upward flow of hot oil, and a stern cooking sectionarranged to connect directly above-said dehydration oil section with thetop outlet for the morsels, whereby in operation steam generated fromthe morsels entering the dehydration section rises with the free upwardflow of hot oil and morsels to the top of the dehydration section, thesteam so generated and the morsels thereafter rising through the cookingsection where the same steam completes the cooking of the morsels.

15. Apparatus according to claim 14, wherein the cooking sectionsunnounts the dehydration section and provides at least one extendedcooking path for the morsels.

16. Apparatus according to claim 14, wherein means are provided forslowing down the rise of the oil and morsels in the dehydration section.

17. Apparatus according to claim 14, wherein the dehydration section issmoothly divergent in the upward sense.

18. Apparatus according to claim 14 further including means for raisingthe morsels through said cooking section.

1. Apparatus for cooking water-impregnated morsels of food whichcomprises an upwardly extending dehydration section having a bottominlet for the morsels and connecting at its top end with a cookingsection, and means for introducing hot oil into the dehydration sectionat such a temperature that, in operation, water in the morsels is turnedinto steam, the morsels and the steam rising in the dehydration sectionto enter the cooking section where heat from the steam is used to cookthe morsels, said cooking section surmounting the dehydration sectionand providing at least one extended cooking path for the morsels, saidextended path being provided by a vibratable spiral elevator. 2.Apparatus according to claim 1, wherein the spiral elevator has a stemwhich extends downwards into the dehydration section.
 3. Apparatusaccording to claim 1, wherein a deflector is provided at the top end ofthe dehydration section for deflecting rising morsels inwards on to theelevator flight.
 4. Apparatus according to claim 1, wherein the elevatorhas a double spiral flight.
 5. Apparatus for cooking water-impregnatedmorsels of food which comprises an upwardly extending dehydrationsection having a bottom inlet for the morsels and connecting at its topend with a cooking section, and means for introducing hot oil into thedehydration section at such a temperature that, in operation, water inthe morsels is turned into steam, the morsels and the steam rising inthe dehydration section to enter the cooking section where heat from thesteam is used to cook the morsels, said cooking section surmounting thedehydration section and including a plurality of vibratable spiralelevatOrs which provide extended cooking paths in parallel relationshipfor the morsels.
 6. Apparatus for cooking water-impregnated morsels offood which comprises an upwardly extending dehydration section having abottom inlet for the morsels and connecting at its top end with acooking section, means for introducing hot oil into the dehydrationsection at such a temperature that, in operation, water in the morselsis turned into steam, the morsels and the steam rising in thedehydration section to enter the cooking section where heat from thesteam is used to cook the morsels, said dehydration section forming oneleg of generally U-form ducting, the other leg which is a dewateringsection having a top inlet for receiving morsels of water-impregnatedfood which also have water on their surfaces, and means for removingwater from the bottom of the ducting.
 7. Apparatus according to claim 6,wherein the ducting adjacent the lower end of the dewatering section hasa section which is shaped to restrict the entry of oil from thedehydration section to the dewatering section.
 8. Apparatus according toclaim 6, wherein a rotatable star-wheel is provided adjacent the lowerend of the dewatering section and arranged to restrict the entry of oilfrom the dehydration section to the dewatering section.
 9. Apparatusaccording to claim 6, wherein the dehydration section is vertical andthe dewatering section is inclined downwards towards the dehydrationsection.
 10. Apparatus according to claim 6, wherein a bend section ofthe ducting which connects the two legs provides a perforated floorabove an outlet for draining off water.
 11. Apparatus according to claim10, wherein the perforated floor forms a shallow depression which facesthe bottom inlet of the dehydration section.
 12. Apparatus according toclaim 10, wherein a nozzle is provided for directing a jet of hot oilagainst the floor.
 13. Apparatus according to claim 12, wherein thenozzle is inclined in the direction of motion of the morsels across thefloor.
 14. Apparatus for cooking water-impregnated morsels of food whichcomprises an upwardly extending dehydration oil section having a bottominlet for the morsels, a bottom inlet for oil, a top outlet for themorsels and a top outlet for oil, the dehydration section being part ofa hot oil circulating system and forming a straight section whichpermits a free upward flow of hot oil, and a steam cooking sectionarranged to connect directly above-said dehydration oil section with thetop outlet for the morsels, whereby in operation steam generated fromthe morsels entering the dehydration section rises with the free upwardflow of hot oil and morsels to the top of the dehydration section, thesteam so generated and the morsels thereafter rising through the cookingsection where the same steam completes the cooking of the morsels. 15.Apparatus according to claim 14, wherein the cooking section surmountsthe dehydration section and provides at least one extended cooking pathfor the morsels.
 16. Apparatus according to claim 14, wherein means areprovided for slowing down the rise of the oil and morsels in thedehydration section.
 17. Apparatus according to claim 14, wherein thedehydration section is smoothly divergent in the upward sense. 18.Apparatus according to claim 14 further including means for raising themorsels through said cooking section.